SDK variables

The x-fern-sdk-variables extension allows you to define variables that are set once during SDK client initialization and automatically used in path parameters across all endpoint calls. This is useful for common parameters like tenant IDs, organization IDs, or environment identifiers that appear in many endpoint paths.

SDK variables are supported in TypeScript (v2.6.3+), Python (v4.24.0+), and Java (v3.6.3+). Only string types are supported.

Configuration

Define variables at the document level using x-fern-sdk-variables, then mark path parameters as variables using x-fern-sdk-variable:

openapi.yml

1 x-fern-sdk-variables:
2   gardenId:
3     type: string
4     description: The unique identifier for your garden
5   zoneId:
6     type: string
7     description: The zone within the garden
8 
9 paths:
10   /gardens/{gardenId}/zones/{zoneId}/plants:
11     get:
12       operationId: list_plants_in_zone
13       parameters:
14         - name: gardenId
15           in: path
16           required: true
17           x-fern-sdk-variable: gardenId
18           schema:
19             type: string
20         - name: zoneId
21           in: path
22           required: true
23           x-fern-sdk-variable: zoneId
24           schema:
25             type: string

SDK usage

Variables become required constructor parameters instead of being passed to individual method calls:

1 const client = new PlantClient({
2   gardenId: "garden_123",
3   zoneId: "zone_456",
4   apiKey: "your-api-key"
5 });
6 
7 const plants = await client.listPlantsInZone();

1	x-fern-sdk-variables:
2	gardenId:
3	type: string
4	description: The unique identifier for your garden
5	zoneId:
6	type: string
7	description: The zone within the garden
8
9	paths:
10	/gardens/{gardenId}/zones/{zoneId}/plants:
11	get:
12	operationId: list_plants_in_zone
13	parameters:
14	- name: gardenId
15	in: path
16	required: true
17	x-fern-sdk-variable: gardenId
18	schema:
19	type: string
20	- name: zoneId
21	in: path
22	required: true
23	x-fern-sdk-variable: zoneId
24	schema:
25	type: string

1	const client = new PlantClient({
2	gardenId: "garden_123",
3	zoneId: "zone_456",
4	apiKey: "your-api-key"
5	});
6
7	const plants = await client.listPlantsInZone();